The Arizona Supreme Court on Thursday ruled that a hotly contested proposition to create a so-called top-two primary system can remain on the Nov. 6 ballot. The ruling came just one day before the hard deadline for printing the ballot, which will have nine propositions.

The Open Elections/Open Government initiative, or Proposition 121, would change the current system -- in which candidates are winnowed down through party primaries -- to one in which all candidates for a given office appear on a single primary-election ballot. Party labels would be optional. The top-two finishers would then advance to the general election. The system would apply to all local, county, state and federal offices, except for presidential elections.

Supporters say the top-two system would lead to more centrist policies by attracting more voters, particularly independents, who typically do not vote in primaries.

Opponents, however, warn of unintended consequences and note that the state of Washington, which has had such a system for several years, has not seen any substantive change.

The Supreme Court's ruling came after the Save Our Vote committee, backed by Republican and Libertarian party members, some Hispanic Democrats and the Arizona League of Women Voters, asked the court for more time to make its case that the citizen initiative lacked the required number of voter signatures to qualify for the ballot.

Opponents alleged that thousands of signatures were gathered by circulators who were not qualified under state law. Last week, a Maricopa County Superior Court judge ruled against the opponents and approved adding the measure to the ballot -- a decision appealed to the high court.

Writing for a three-judge Supreme Court panel, Vice Chief Justice Scott Bales rejected opponents' arguments. Among other things, he noted that opponents did not object last week when Superior Court Judge John Rea set aside four hours for the case, dividing the time equally between the two sides.

When Save Our Vote did ask for more time late in the trial, it did not lay the foundation for its evidence that 6,000 sheets of voter signatures were gathered by unqualified circulators, Bales wrote.

The committee also did not argue that its two-hour allotment hurt its ability to make its case, wrote Bales, who was joined by Chief Justice Rebecca White Berch and Justice Robert Pelander

Aaron Baer, a spokesman for Save Our Vote, called the ruling a "disappointment" that sets a harmful precedent. That's because the two-month time frame for verifying petition signatures is a brief window for weeding out unqualified voter signatures.

"A group is able to flood the system with enough bad petition circulators and bad petition signers, and there's nothing we can do about it," he said.

Baer said the committee is convinced the initiative included signatures gathered by criminals but lacked the time to prove this to the court.

Although the lower court did toss more than 2,000 signatures gathered by three unqualified circulators, it was not enough to derail the initiative.

Committee Chairman Paul Johnson said the high-court ruling ends a string of hurdles that dogged the effort even before supporters submitted nominating petitions.

"I've personally been trying to pull myself off the ceiling, I'm so excited," said Johnson, a former Phoenix mayor.

He acknowledged there are problems with using a paid contractor to gather signatures, but he noted the committee turned in one questionable circulator to elections officials and did not challenge the lower-court judge's decision to disqualify three others.

He and other supporters believe if the top-two primary system attracts more independent voters, a growing segment of registered voters, it could usher in candidates more attentive to the middle of the electorate. The primary system favors candidates who play to the partisan fringes of their party, he said.

The Open Elections message is simple, he said: "Why shouldn't every voter have the right to vote in every election?"

Opponents, he said, will try and confuse voters, which was apparent when supporters fought off a string of lawsuits and an aborted effort by the Legislature to put a competing measure on the ballot.

Last month, Save Our Vote had tried to block the measure from the ballot by arguing it violated the state Constitution's single-subject rule, which says ballot measures should tackle only one topic. That case also went to the state Supreme Court, which ruled the measure complied with state law.

Opponents say Arizona could take a lesson from neighboring California, which in June conducted its first top-two primary. In one congressional race in a district with a strong Democratic and Latino population, two Republicans advanced to the general election, defeating Latino candidates.

It's an example of the unintended consequences of a government-reform measure, they say. The political parties also object to the idea because it could dilute party influence.

In addition to Prop. 121, voters in November will consider eight other measures. They include a permanent 1-cent-per-dollar increase in the state sales tax to pay for education and infrastructure, a tax break for business gear and a declaration of state sovereignty.